This pilot research program proposal responds to a listed topic area (HIV/AIDS and aging) und& NIA Program Announcement 99-049. The applicant's broad, long-term objectives include the elucidation of the combined effects of HIV/AIDS and aging on cognitive functioning. AIDS in adults over the age of 50 years has more than tripled over the last several years and current estimates suggest that 10% of adults with MDS are over 50 years old and 3% are over 60 years old. However, most neuropsychological studies of HIV/AIDS have focused on younger adults. In addition, although an AIDS-related dementia appears to be more prevalent in older adults, little research has focused on specific cognitive processing abilities in older HIV+ adults. Specific aims of the present proposal include the examination of information processing (visual selective attention), workload, and multi- task performance (single, dual, and multi-task task conditions) in younger and older HIV- and HIV+ adults. Performance will be assessed on a desktop computer using SuperLab software (developed at NIH) and the Multi-Attribute Task Battery (developed at NASA Langley). Workload will be measured with the NASA TLX, comprising of several subjective rating scales. Previous results suggest that psychomotor speed and attention ability are differentially disrupted in older HW+ adults, especially in those with AIDS. Workload is a useful human factors concept that can differentiate subject state/effort and subject performance. Because many HIV+ adults perform normal behaviors,(such as driving a car), multi-task performance is assessed to determine deficiencies in more realistic performance situations. The central hypothesis is that cognitive deficits will be largest in older HIV+ adults, especially in MDS cases. Differential deficits in older HIV+ adults are also predicted to increase with task difficulty and task complexity. Deficits in certain aspects of selective attention (such as visual search but, perhaps not filtering) are proposed to predict declining multi- task performance. And HIV-related differences in subjective workload will be compared to HIV-related differences in performance.